Electrical connector with a helical bimetal overload



Dec. 21, 1965 K. M- DELAFRANGE ELECTRICAL CONNECTOR WITH A HELICAL BIMETAL OVERLOAD Filed Feb. 24, 1964 BY 5&9 M I ATTORNEY United States Patent Ofifice 3,225,162 ELECTRICAL CONNECTOR WITH A HELICAL BIMETAL OVERLOAD Kenneth M. Delafrange, 96 Washington Ave., Westwood, NJ. Filed Feb. 24, 1964, Ser. No. 346,780 7 Claims. (Cl. 200-1155) This invention relates to improvements in safety electric connectors protective against overloading electric conductors in wiring systems of buildings and in other uses. More particularly, it relates to electrical connectors interposed between input circuit wiring from an electric power source and branch output circuits connected thereto and to appliances and other power translating devices.

While there are other causations of failure and damage from overloading distribution circuits in installed wiring systems, by far the most common overload causation is that of detachable connection of current consuming means with branch supply circuits of the system at terminal connector outlets. This invention contemplates control of such circuits against overloading which often results in fires and other damage occasioned by overloading connections at such terminal outlets.

It is, therefore, an object of the invention to provide improved electrical connector devices which, in use, will protect electric current supply wiring against abnormal heating and damage from overload conditions.

A further object of the invention is provision of improved electrical connectors providing branch output circuit extensions with at least one of the conductor means therethrough constituting also a thermal responsive circuit cutout and a circuit reclosing means.

A more specific object of the invention is provision of electrical connectors having directly in one of the conducting lines therethrough a helical Nichrome wire conductor operated switch automatically operable under current flow conditions in the line.

The foregoing and further objects and advantages of the invention will be apparent from the following specification and the drawings forming a part thereof wherein:

FIG. 1 is a side view of a three way branch circuit plug connector embodiment of the invention, partly broken away, showing in a conductor means therethr-ough .a spiral conductor operated circuit cutout and circuit restoring arrangement in normal closed position.

FIG. 2 is a partly broken front view of the structure of FIG. 1.

FIG. 3 is a side view corresponding to FIG. 1 but showing the conductive circuit cutout constructional arrangement in open circuit position.

FIG. 4 is a top view, partly broken, of a multiple tap terminal outlet Wall receptacle embodiment of the invention.

-FIG. 5 is a fragmentary enlarged perspective view showing the structural combination relationship of the linearly expansible spring conductor operated cutout and the associated conductor bar and contact means of FIG. 4, with the cutout being illustrated in open position.

In FIGS. 1-3 of the drawing a plural conductor multiple circuit attachment plug 1 provides two sides and one bottom branch output circuit connector receptacles in each of which are provided in conventional manner two spaced and independent contacts 2 engageable by plug contacts passing through spaced slots in the insulating 3,225,162 Patented Dec. 21, 1965 body of the structure. Contacts 2 are parts of separate contact assemblies each inclusive of a conductor bar 3 and electrical connections to associated respective projecting connector blade contacts 4 and 5 for circuit continuation through plug 1 by insertion of the blades into a terminal outlet of a wiring system. Blade contact 4 and its associated connection and contact assembly may be permanently connected in customary manner and are not illustrated in detail. Blade 5, however, is structurally different, having its inner end portion bent to provide anchoring and spring bearing flange portion 6, and further differs structurally from conventional contacts by its incorporation as a terminal part of a normally closed conductive cutout directly in circuit between blade contact 5 and its conductively associated bus bar 3 and a contact 2 thereon in each of the output circuit receptacles.

Contact 5 has fixed thereto at its inner end portion a helical wire spring form conductor 7 with the connected end coil of the spring form having underlying bearing against flange portion 6. Conductor 7 carries in fixed connection therewith at its free end a transverse contact bar 8 provided at its free end with a fixed contact element 9. Conductor bar 3 of the branch contact assembly has fixed thereto an upstanding conductor bar support 10 having its free end angularly bent and provided with fixed contact 11 so as to overlie and normally engage bar 8 and contact 9, this normal engagement being maintained under a slight calculated tension of spring form conductor 7 sufficient to normally hold the contacts 9 and 11 in closed position. This conductor 7 is made of high temperature metal or alloy retentive of strength when heated and difiering conductively and in performance under current flow therethrough from its associated conductors which are of relatively soft and conventional low resistance character. Nichrome wire is used in conductor 7 it having been found to have the most desirable operational characteristics under passage of current therethrough when in helical spring form, and, the gauge of the wire is predetermined by the maximum current value at which protective cutout operation is desired and in which minimum of impedance is involved.

The connector of the foregoing description is designed to operate in the following manner. Inserted into a terminal outlet connected with a power source, normal operation is simply that of providing branch output circuit or circuits from source. However, if there is or are connected therewith current consuming means of greater load capacity than that for which the connector is designed, the added resultant current fiow quickly changes the static condition of the helical spring form conductor 7 causing it to heat and expand in linear movement to break engagement of contacts 9 and 11, thus opening the circuit. The heating characteristics of the Nichrome wire or the like under passage of the abnormally increased current produces quick elongation action of the spring for-m conductor to open the cutout switch so .as to minimize and stop heat storage in circuit wiring. Also, in cooling or circuit breaker reclosing operation heat storage in supply lines has longer time for dissipation.

In an embodiment of the invention in FIGS. 4 and 5, a wall type terminal receptacle or outlet 14 having branch circuit outlets 15 and 16 is shown connected to power service wires 17 and 18 through binding terminals 19 and 20 and multiple tap connections are provided at the outlets by pairs of contacts 22 connected to and supported by conductor bars such as 21. One of these bars 21 is provided with an angularly bent extension flange 23 at one end mounting if desired a contact 24. Adjacent the bar 21, insulated therefrom and substantially parallel thereto, a helical spring form wire conductor 26 similar to that hereinbefore described and of Nichrome wire is fixed at one end to binding terminal portion 27 by suitable fastening 27 and carries at its free end the transverse conducting switch bar 28 mounting contact 29 normally overlying and in contact with the contact 24 on conductor bar 21. Conductor 26 is disposed in a guide recess 30 in the insulation body of the outlet with its free end switch bar 28 and contact 29 disposed in an enlarged chamber portion of the recess 30 provided for free movement of contact 29 into and out of contact with the contact 24 in response to linear movement of expansion of the conductor 26 in heating and cooling.

The operation of the cutout is as previously described in connection with the structure of FIG. 1, namely, the cutout switch remains normally closed as illustrated in FIG. 4 when output circuit loads connected to outlets and/or 16 draw current within the predetermined range for which the arrangement is designed. When attachment plug connected output circuits connected with the outlets are inclusive of appliances or other power translating means using current greater than that for which the connectors are designed this overload causes abnormal heating of the conductor 26 causing it to expand linearly to separate the contacts 24 and 29 to open the circuit from supply lines, thus preventing overheating of such lines. When disconnected, cooling of the spring form conductor 26 causes it to again force engagement of the contacts 24 and 29. The stoppage of current supply to the translating devices or the like informs the user of overload conditions and the necessity of correction of the fault. The thermal responsive conductive means in the connectors are normally so designed as to be operative as a cutout at current values slightly below those which would result in blown-out fuses and the like.

It will be apparent from the foregoing description of the embodiments of the invention selected for illustration that the plug type connectors of FIGS. l3 will prove protective of wiring systems using ordinary terminal outlets, and, that the use of terminal outlets such as illustrated in FIG. 4 will be protective of Wiring installations where ordinary plug connected loads without the protective control feature therein are connected with the outlets. The invention is not limited to connectors with connecting contacts of the exact kind illustrated for other well known plug-in and socket contacts may be employed. When attachment plugs of the screw shell type are involved the conductive path therethrough inclusive of the thermal cutout is that from the central terminal of the plug.

While the invention has been described in connection with specific embodiments of the invention the words are those of description and not of limitation, for structural modifications within the purview and scope of the appended claims are contemplated without departure from the true scope and spirit of the invention.

I claim:

1. In combination with multiple terminal conductors of an electric power input circuit, a current overload control connector device connected with said conductors and having attachment plug receiving contacts adapted for separable connection with associated attachment plug contacts in a power consuming output circuit extension, said connector having an insulating housing and separate electric current conductive assemblies including said plug receiving contacts therein, one of said conductive assemblies having directly embodied therein a thermal cutout comprising a fixed contact and a movable contact normally engaged therewith and a helical spring form conductor mounting the movable contact at a free end thereof and conductively fixed at the other end against movement, said helical spring form conductor normally maintaining the contacts in engagement Within a predetermined normal load current flow range but subject to linear expansion to separate the contacts under heat generated in the helical conductor by flow therethrough of an overload current above said range.

2. The combination as defined in claim 1 characterized by a helical spring form conductor of Nichrome wire.

3. An overload electric current controlling connector comprising an insulating housing, multiple and separate electric current conductive assemblies including contacts for detachable connection with contacts of an attachment plug in a power consuming output circuit extension from the connector, one of said conductive assemblies having directly therein as a part thereof a fixed switch contact, a helical spring form Nichrome wire conductor of predetermined size and conductive capacity conductively fixed against movement at one end and supporting at a free end a movable switch contact normally engaged with the fixed switch contact, said helical spring form conductor maintaining the switch contacts in conductive engagement throughout a predetermined safety current flow range under normal load conditions but subject to linear expansion to separate the switch contacts caused by heat generated in the helical conductor by flow therethrough of overload current above said range, and means for joining the connector with plural terminal conductors of an input power circuit.

4. An electric attachment plug connector having a plurality of exposed electric current conductive contacts for detachable connections with contacts in an outlet con nector of a power supply circuit and separate and individual conductive means connected respectively with said first mentioned contacts for output current supply connections to electric power translating means, one of said conductive means being inclusive of a fixed contact and a helical spring form Nichrome wire conductor of predetermined size and current carrying capacity having one end conductively fixed against movement and a free end provided with contact means normally held by the spring form conductor in engagement with the fixed contact, said helical spring form conductor maintaining engagement of the contacts throughout a predetermined normal load safety current flow range but subject to linear expansion under abnormal heat generated in the helical conductor by overload current flow therethrough to cause opening of said contacts to break the circuit.

5. A combined electric attachment plug and multiple branch circuit connector comprising a plug portion having exposed spaced blade contacts for detachable connection with contacts in an outlet connector of a power supply circuit, and a plurality of branch circuit supply outlets each provided with spaced contacts each being connected with a blade contact of the plug portion, a thermally responsive circuit breaker and maker in one of the connections between the plug portion blade contact and its associated outlet contacts, said circuit breaker and maker comprising an incircuit helical spring form wire conductor conductively fixed at one end and carrying at a free end switch contact means and a fixed contact in normal engagement with the spring form wire carried contact means, said helical spring form conductor maintaining engagement of the contacts throughout a predetermined safety current fiow range without abnormal heating but subject to linear expansion under abnormal heat generated in the helical conductor to open the contacts when overload current flows through the conductors.

6. A combined electric connector as defined in claim 5 characterized by a helical spring form connector of Nichrome wire.

7. An electric supply circuit outlet connector for overload control in electric wiring, an insulating housing providing multiple tap receptacles for attachment of branch output circuit connections, a pair of spaced conductor assemblies each mounting contacts disposed in the receptacles, one of said conductor assemblies having a conductive connecting member angularly bent at one end and there provided with a switch contact, a helical spring form conductor fixed at one end to a binding post structure for connection to circuit wire and having a free end provided with a transverse switch contact means in normal engagement with said first mentioned switch contact, said helical spring form conductor being of Nichrome wire maintaining the switch contacts in engagement when current flow therethrough is within a predetermined safety range but operative through lineal expansion to open the contacts when overload current flow therethrough is above said safety range, the other of said conductor assemblies being permanently connected to a supply circuit connector binding post.

No references cited.

BERNARD A. GILHEANY, Primary Examiner. 

1. IN COMBINATION WITH MULTIPLE TERMINAL CONDUCTORS OF AN ELECTRIC POWER INPUT CIRCUIT, A CURRENT OVERLOAD CONTROL CONNECTOR DEVICE CONNECTED WITH SAID CONDUCTORS AND HAVING ATTACHMENT PLUG RECEIVING CONTACTS ADAPTED FOR SEPARABLE CONNECTION WITH ASSOCIATED ATTACHMENT PLUG CONTACTS IN A POWER CONSUMING OUTPUT CIRCUIT EXTENSION, SAID CONNECTOR HAVING AN INSULATING HOUSING AN SEPARATE ELECTRIC CURRENT CONDUCTIVE ASSEMBLIES INCLUDING SAID PLUG RECEIVING CONTACTS THEREIN, ONE OF SAID CONDUCTIVE ASSEMBLIES HAVING DIRECTLY EMBODIED THEREIN A THERMAL CUTOUT COMPRISING A FIXED CONTACT AND A MOVABLE CONTACT NORMALLY ENGAGED THEREWITH AND A HELICAL SPRING FORM CONDUCTOR MOUNTING THE MOVABLE CONTACT AT A FREE END THEREOF AND CONDUCTIVELY FIXED AT THE OTHER END AGAINST MOVEMENT, SAID HELICAL SPRING FORM CONDUCTOR NORMALLY 